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Subject: Re: [OMPI users] Problem running an mpi applicatio​n on nodes with more than one interface
From: Richard Bardwell (richard_at_[hidden])
Date: 2012-02-17 05:36:49


I had exactly the same problem.
Trying to run mpi between 2 separate machines, with each machine having
2 ethernet ports, causes really weird behaviour on the most basic code.
I had to disable one of the ethernet ports on each of the machines
and it worked just fine after that. No idea why though !

  ----- Original Message -----
  From: Jingcha Joba
  To: users_at_[hidden]
  Sent: Thursday, February 16, 2012 8:43 PM
  Subject: [OMPI users] Problem running an mpi applicatio​n on nodes with more than one interface


  Hello Everyone,
  This is my 1st post in open-mpi forum.
  I am trying to run a simple program which does Sendrecv between two nodes having 2 interface cards on each of two nodes.
  Both the nodes are running RHEL6, with open-mpi 1.4.4 on a 8 core Xeon processor.
  What I noticed was that when using two or more interface on both the nodes, the mpi "hangs" attempting to connect.
  These details might help,
  Node 1 - Denver has a single port "A" card (eth21 - 25.192.xx.xx - which I use to ssh to that machine), and a double port "B" card (eth23 - 10.3.1.1 & eth24 - 10.3.1.2).
  Node 2 - Chicago also the same single port A card (eth19 - 25.192.xx.xx - again uses for ssh) and a double port B card ( eth29 - 10.3.1.3 & eth30 - 10.3.1.4).
  My /etc/host looks like
  25.192.xx.xx denver.xxx.com denver
  10.3.1.1 denver.xxx.com denver
  10.3.1.2 denver.xxx.com denver
  25.192.xx.xx chicago.xxx.com chicago
  10.3.1.3 chicago.xxx.com chicago
  10.3.1.4 chicago.xxx.com chicago
  ...
  ...
  ...
  This is how I run,
  mpirun --hostfile host1 --mca btl tcp,sm,self --mca btl_tcp_if_exclude eth21,eth19,lo,virbr0 --mca btl_base_verbose 30 -np 4 ./Sendrecv
  I get bunch of things from both chicago and denver, which says its has found components like tcp, sm, self and stuffs, and then hangs at
  [denver.xxx.com:21682] btl: tcp: attempting to connect() to address 10.3.1.3 on port 4
  [denver.xxx.com:21682] btl: tcp: attempting to connect() to address 10.3.1.4 on port 4

  However, if I run the same program by excluding eth29 or eth30, then it works fine. Something like this:
  mpirun --hostfile host1 --mca btl tcp,sm,self --mca btl_tcp_if_exclude eth21,eth19,eth29,lo,virbr0 --mca btl_base_verbose 30 -np 4 ./Sendrecv
  My hostfile looks like this
  [sshuser_at_denver Sendrecv]$ cat host1
  denver slots=2
  chicago slots=2

  I am not sure if I have to provide somethbing else. Please if I have to, please feel to ask me..
  thanks,
  --
  Joba


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